KR20150127142A - Method for manufacturing polarizing laminated film and method for manufacturing polarizing plate - Google Patents

Abstract

The present invention provides a method for preparing a coating solution, comprising the steps of: preparing a coating solution in a reservoir of a coating machine; A resin layer forming step of supplying a coating liquid onto one side or both sides of a base film from a storage vessel through a coating head of a coating machine and coating the same to form a resin layer to obtain a laminated film; A stretching step of stretching the laminated film to obtain a stretched film; And a dyeing step of dying the resin layer of the stretched film with a dichroic dye to obtain a polarizing laminated film. In the coating liquid preparing step and / or the resin layer forming step, the coating liquid is fed at least once through a pipe, A method of producing a polarizing laminated film in which a part of the coating liquid is taken out of the pipe, and a polarizing plate production method using the polarizing laminated film obtained by the above method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate laminated film,

The present invention relates to a method for producing a polarizing laminated film and a method for producing a polarizing plate.

The polarizing plate is widely used as a polarizing light supplying element in a liquid crystal display and also as a polarizing light detecting element. Conventionally, as a polarizing plate, a polarizing film mainly composed of a polyvinyl alcohol-based resin is bonded to a protective film made of triacetyl cellulose or the like through an adhesive. Recently, a liquid crystal display device has been developed , And further development to a large-sized television, the thickness of the polarizer is required to be reduced.

However, the polarizing film is produced by stretching and staining a film original of a polyvinyl alcohol-based resin (usually about 75 탆 in thickness), and the thickness of the stretched film is usually about 30 탆. Such thinning has been problematic in terms of productivity, for example, in that the film tends to be broken at the time of stretching.

Thus, a polyvinyl alcohol-based resin layer is formed by coating a coating liquid containing a polyvinyl alcohol-based resin on a base film to obtain a laminated film, and then the laminated film is subjected to stretching and dyeing treatment to form a polyvinyl alcohol- A method of producing a laminated film or a polarizing plate having a polarizing layer in which a resin layer is provided with a polarizing function to form a polarizing layer has been proposed (see, for example, Japanese Patent Application Laid-Open Nos. 2009-93074 and 2001-150313 (Patent Document 2)].

According to the method of forming a polarizer layer by coating a coating liquid containing a polyvinyl alcohol-based resin as described in the above Patent Documents 1 and 2, A thin polarizer layer can be obtained, which is advantageous from the viewpoint of thinning of the polarizer.

However, the coating liquid containing the polyvinyl alcohol-based resin is liable to foam easily, and once the foam is formed, the foam is hardly lost due to the surfactant action of the polyvinyl alcohol-based resin. The resin layer obtained by coating a coating solution containing such bubbles on a base film contains a large amount of bubbles. The polarizing laminated film or polarizing plate obtained by stretching and staining the laminated film thus obtained does not exhibit good polarization performance and appearance Therefore, it is difficult to use as a product. Therefore, the base film of the portion coated with the coating liquid containing bubbles can not be discarded.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a polarizing laminated film or a polarizing plate producing method comprising a step of forming a resin layer by coating a coating liquid containing a polyvinyl alcohol- (Time) in which the coating liquid containing bubbles is supplied from the coating machine to the base film at the time of coating the coating liquid can be minimized (shortened), whereby the loss of the base film can be effectively reduced There is a way to provide.

The present invention includes the following.

≪ 1 > A method for preparing a coating liquid, comprising the steps of: preparing a coating liquid containing a polyvinyl alcohol-based resin in a reservoir of a coating machine;

The coating liquid is supplied from at least one surface of the base film through the coating head of the coating machine from the storage tank and is then dried to form a polyvinyl alcohol based resin layer to form a resin layer The process,

A stretching step of stretching the laminated film to obtain a stretched film,

A dyeing step of obtaining a polarizing laminated film by dying a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer

And,

Wherein the coating liquid is transferred at least once through a pipe in the coating liquid preparing step and / or the resin layer forming step, and a part of the coating liquid is taken out from the pipe during the step of preparing the polarizing laminated film.

≪ 2 > The coating machine according to any one of claims 1 to 3, further comprising: a first pipe connecting the storage tank and the coating head; and a second pipe branched from the first pipe,

The method according to < 1 >, wherein a part of the coating liquid is taken out through the second pipe while transferring the coating liquid from the storage tank toward the coating head.

&Lt; 3 > The method according to < 2 >, wherein a part of the coating liquid is taken out when the coating liquid is transferred through the inner space not filled with the coating liquid as the space of the first pipe.

&Lt; 4 > The method according to any one of < 1 > to < 3 >, wherein the laminated film is stretched at a draw ratio of more than 5 times.

<5> The method according to any one of <1> to <4>, wherein the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film in the resin layer forming step.

<6> The method according to any one of <1> to <5>, wherein the thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 to 30 μm.

<7> The method according to any one of <1> to <6>, wherein the base film is made of a polypropylene type resin.

<8> A method for producing a polarizing laminated film, comprising the steps of: preparing a polarizing laminated film by the method described in any one of <1> to <7>

A step of bonding a protective film to the polarizer layer of the polarizing laminated film to obtain a bonded film,

A step of peeling the base film from the bonded film

And a polarizing plate.

According to the method of the present invention, since the loss of the base film can be reduced, a polarizing laminated film or a polarizing plate can be produced with good yield.

Fig. 1 is a flowchart showing a preferred embodiment of a method for producing a polarizing laminated film and a method for producing a polarizing plate according to the present invention.
2 is a schematic view showing an example of the configuration of a coating machine capable of suitably carrying out the method for producing a polarizing laminated film and the method for producing a polarizing plate according to the present invention.

Hereinafter, the method for producing a polarizing laminated film and the method for producing a polarizing plate according to the present invention will be described in detail with reference to embodiments.

&Lt; Method for producing a polarizing laminated film &

Fig. 1 is a flowchart showing a preferred embodiment of a method for producing a polarizing laminated film and a method for producing a polarizing plate according to the present invention. The method for producing a polarizing laminated film of this embodiment includes the following steps [1] to [4] in this order.

[1] Prepare a coating solution containing a polyvinyl alcohol-based resin in a reservoir of a coating machine.

[2] From the storage tank, the coating liquid is supplied to at least one surface of the substrate film through the coating head of the coating machine, and then the coating liquid is dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film Forming process S20.

[3] A stretching step S30 for obtaining a stretched film by stretching the laminated film.

[4] A dyeing step S40 for obtaining a polarizing laminated film by dying a polyvinyl alcohol-based resin layer of a drawn film with a dichroic dye to form a polarizer layer.

In at least one of the coating solution preparing step S10 and the resin layer forming step S20, the coating solution is fed at least once through the pipe, and a part of the coating solution is taken out from the middle of the pipe.

As described later, in the polarizing plate of the present embodiment, a protective film is bonded on the polarizing layer of the polarizing laminated film obtained by performing up to the dyeing step S40 to obtain a bonded film (bonding step S50) (Peeling step S60).

Hereinafter, the steps S10 to S40 of the method for producing a polarizing laminated film of the present embodiment will be described in more detail.

[1] Preparation of coating liquid S10

This step is a step of preparing a coating solution containing a polyvinyl alcohol-based resin in a reservoir of a coating machine.

(Coating liquid containing a polyvinyl alcohol-based resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and derivatives thereof. Examples of derivatives of polyvinyl alcohol resins include polyvinyl formal, polyvinyl acetal and the like, modified polyvinyl alcohol resins with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid; Acrylamide, and the like. The modification ratio is preferably less than 30 mol%, more preferably less than 10 mol%. When the modification is carried out in an amount exceeding 30 mol%, it is difficult to adsorb the dichroic dye and the polarization performance may be lowered. Of the polyvinyl alcohol-based resins described above, polyvinyl alcohol resins are preferably used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10,000, more preferably in the range of 1,000 to 10,000, more preferably in the range of 1,500 to 8,000, and more preferably in the range of 2,000 to 5,000 Is most preferable. The average degree of polymerization can be determined by the method described in JIS K 6726-1994 &quot; Polyvinyl alcohol test method &quot;. When the average degree of polymerization is less than 100, it is difficult to obtain a desired polarizing performance. When the average degree of polymerization is more than 10,000, the solubility in a solvent deteriorates and it becomes difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The degree of saponification is preferably 80 mol% or more, more preferably 90 mol% or more, particularly preferably 94 mol% or more. If the degree of saponification is too low, there is a possibility that the water resistance and humidity resistance of the polarizing laminated film or polarizing plate may become insufficient. If the degree of saponification is excessively high, the dyeing speed is slowed. In order to give sufficient polarizing performance, the production time may be prolonged, and in some cases, sufficient polarization performance (e.g., Or a polarizer layer having a polarizer layer having a refractive index different from that of the polarizer layer can not be obtained. Therefore, the saponification degree is more preferably 99.5 mol% or less and 99.0 mol% or less.

The degree of saponification indicates the unit ratio (mol%) of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin as the raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification treatment, The following formula:

Saponification degree (mol%) = [(number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)] x 100

.

The higher the degree of saponification, the higher the ratio of hydroxyl groups, which means that the proportion of acetic acid groups that inhibit crystallization is smaller. The saponification degree can be determined by the method described in JIS K 6726-1994 &quot; Polyvinyl alcohol test method &quot;.

As the polyvinyl acetate resin, a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, with other monomers copolymerizable with vinyl acetate, and the like are exemplified. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

Examples of commercial products of polyvinyl alcohol resins that can be suitably used are "PVA 124" (saponification degree: 98.0 to 99.0 mol%) and "PVA117" (saponification degree: 98.0 (Saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 to 96.0 mol%) and "PVA617" (saponification degree: 94.5 to 95.5 mol%); AH-26 "(saponification degree: 97.0 to 98.8 mol%)," AH-22 "(saponification degree: 97.5 to 98.5 mol%)," NH-18 " : 98.0 to 99.0 mol%) and "N-300" (saponification degree: 98.0 to 99.0 mol%); (Saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5 to 95.5 mol%), and JM-26 (saponification degree: 95.5 mol%) manufactured by Nippon SAKUBO Co., JF-17L "(saponification degree: 98.0 to 99.0 mol%) and" JF-17L "(saponification degree: 98.0 to 99.0 mol% Mol%) and "JF-20" (saponification degree: 98.0 to 99.0 mol%).

The coating liquid may contain an additive such as a plasticizer and a surfactant if necessary. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

(Coating machine)

Conventionally known ones can be appropriately selected and used as the coating machine. Examples of the coating machine include, for example, a wire bar coater; A roll coater such as a reverse coater or a gravure coater; Die coater; Comma coater; Lip coater; Spin coater; Screen coater; Fountain coater; Dip coater; Spray coaters.

The coating machine has at least a coating head for supplying the coating liquid onto the base film and a storage tank for storing the coating liquid. As shown in Fig. 2 showing an example of a configuration of a coating machine capable of suitably carrying out the method for producing a polarizing laminated film according to the present embodiment and the method for producing a polarizing plate, in general, And a pump for transporting the coating liquid.

2, the coating machine 1 comprises a coating head 5 for supplying a coating liquid onto a base film; A storage tank (tank) 2 for storing the coating liquid; A filter 4 disposed immediately in front of the coating head 5 to remove dust or the like in the coating liquid; And a pump 3 for delivering the coating solution in the storage tank 2. The storage tank 2 and the coating head 5 are connected to each other by a first pipe 6. The pump 3 and the filter 4 are interposed in the first pipe 6. [ The first pipe 6 is a conveying pipe for the coating liquid from the storage tank 2 to the coating head 5. A second pipe 7 branched from the filter 4 and the coating head 5 is connected to the first pipe 6.

The configuration and material of the coating head 5, the filter 4 and the first pipe 6 may be conventional in a coating machine. The configuration and material of the pump 3 may be the same as those of the coating machine. Among them, a pump having less leakage of air, for example, a mono pump and a diaphragm pump can be suitably used. The structure and material of the storage tank 2 may be the same as those of the coating machine, and the storage tank 2 may be a container itself for storing or transporting the coating liquid after preparation, such as a drum or a container.

It is preferable that the discharge port of the storage tank 2 for discharging the coating liquid is formed in the lower part of the storage tank 2. [ When there is an outlet at the top, the pump 3 is likely to be subjected to a load, particularly when the viscosity of the coating liquid is high. On the other hand, a defoaming tank (tank capable of performing vacuum defoaming or the like) may be used as the storage tank 2.

In this step, a coating solution is prepared in the storage tank 2 of the coating machine 1. The preparation of the coating liquid can be prepared, for example, in the following manner.

(a) A coating liquid contained in a container for storing or transporting, using a pump or the like, is transferred to the storage tank 2.

(b) The container itself for preserving or transporting the coating solution after preparation is connected to the pump 3.

(c) The storage tank 2 connected to the pump 3 or the container is replaced with a separate storage tank 2 for storing the coating liquid or a separate container.

The above methods (a) to (c) can also be used when the coating liquid is reduced and the coating liquid is replenished to the storage tank 2. [ In the method (a), it is preferable to prevent the liquid from splashing on the surface of the coating liquid by using a pump or the like, and to suppress the generation of bubbles as much as possible, since bubbles tend to occur when the coating liquid is manually poured from above. There is no particular limitation on the constitution or material of the pump to be used and the piping or the like attached thereto. In this way, when the coating liquid is transported through the piping, liquid removal described later may be performed.

[2] Resin layer formation step S20

In this step, a coating liquid is supplied from the storage tank 2 of the coating machine 1 through the coating head 5 to coat a polyvinyl alcohol resin layer on at least one side of the base film to obtain a laminated film Process. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizer layer through the stretching step S30 and the dyeing step S40. The polyvinyl alcohol-based resin layer can be formed by coating a coating solution on one side or both sides of a base film and drying the coating layer. According to this method, since the thickness of the polyvinyl alcohol-based resin layer and further the polarizer layer can be made small, it is advantageous in reducing the thickness of the polarizing laminated film and the polarizing plate.

According to the present invention, a coating liquid containing no bubbles (or having a sufficiently small amount of bubbles) can be supplied onto the base film from the beginning of the coating process for applying the coating liquid to the base film in order to carry out the liquid removal.

(Substrate film)

The base film may be composed of a thermoplastic resin, and it is preferable that the base film is made of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such a thermoplastic resin include polyolefin resins such as a chain polyolefin resin and a cyclic polyolefin resin (norbornene resin and the like); Polyester-based resin; (Meth) acrylic resins; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polycarbonate resin; Polyvinyl alcohol-based resin; Polyvinyl acetate resin; Polyarylate resins; Polystyrene type resin; Polyether sulfone type resin; Polysulfone resins; Polyamide based resin; Polyimide resin; And mixtures and copolymers thereof, and the like.

The base film may be a single layer structure composed of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a multilayer structure in which a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated.

Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins. A base film composed of a chain polyolefin-based resin is preferable because it is easy to stably stretch at a high magnification. Among them, the base film is preferably a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), a polyethylene resin (a copolymer mainly composed of polyethylene resin or ethylene which is a homopolymer of ethylene) And the like.

A copolymer mainly composed of propylene, which is one of examples suitably used as a thermoplastic resin constituting the base film, is a copolymer of propylene and other monomers copolymerizable therewith.

Examples of other monomers copolymerizable with propylene include ethylene and? -Olefins. As the? -olefin, an? -olefin having 4 or more carbon atoms is preferably used, and more preferably an? -olefin having 4 to 10 carbon atoms. Specific examples of the? -Olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; Vinyl cyclohexane and the like. The copolymer of propylene and other monomer copolymerizable therewith may be a random copolymer or a block copolymer.

The content of the other monomer in the copolymer is, for example, from 0.1 to 20% by weight, and preferably from 0.5 to 10% by weight. The content of other monomers in the copolymer can be determined by infrared (IR) spectrum measurement according to the method described in "Polymer Analysis Handbook" (1995, published by Kinokuniya Shoten), page 616.

Of the above, propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer or propylene-ethylene-1-butene random copolymer are preferably used as the polypropylene type resin.

The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. A base film made of a polypropylene resin having substantially isotactic or syndiotactic stereoregularity is relatively easy to handle and has excellent mechanical strength under a high temperature environment.

The base film may be composed of one kind of chain polyolefin series resin, or may be composed of a mixture of two or more chain type polyolefin series resins, or may be composed of a copolymer of two or more chain type polyolefin series resins.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized with cyclic olefin as a polymerization unit, and examples thereof include those described in JP-A-1-240517, JP-A-3-14882, And resins described in publications and the like. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically, random copolymers) of cyclic olefins and chain olefins such as ethylene and propylene, Graft polymers modified with carboxylic acids or their derivatives, and hydrides thereof. Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

Various products of cyclic polyolefin resin are commercially available. (Commercially available from TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co.), &quot; ATON &quot; (manufactured by JSR Corporation), and &quot; ZEONOR "(manufactured by Nippon Zeon Co., Ltd.)," ZEONEX "(manufactured by Nippon Zeon Co., Ltd.), and" APEL "(manufactured by Mitsui Chemicals, Inc.).

(Manufactured by Sekisui Chemical Co., Ltd.), "SCA40" (manufactured by Sekisui Chemical Co., Ltd.), "Zeonoa Film" (manufactured by Nippon Zeon Co., Ltd.) Or the like may be used as the substrate film.

The base film may be composed of one cyclic polyolefin resin or a mixture of two or more cyclic polyolefin resins or a copolymer of two or more cyclic polyolefin resins.

The polyester-based resin is a resin having an ester bond, and is generally composed of a polycondensation product of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, dimethyl naphthalenedicarboxylate and the like. As the polyhydric alcohol, a dihydric diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

As a representative example of the polyester-based resin, polyethylene terephthalate which is a polycondensation product of terephthalic acid and ethylene glycol can be mentioned. The polyethylene terephthalate is a crystalline resin, but it is easy to carry out the treatment such as drawing in the state before the crystallization treatment. If necessary, the crystallization treatment can be performed by a heat treatment at the time of stretching or after stretching. Also, copolymerized polyesters having reduced crystallinity (or made amorphous) by copolymerizing monomers of another species to the skeleton of polyethylene terephthalate are also suitably used. Examples of such resins include copolymers obtained by copolymerizing cyclohexane dimethanol or isophthalic acid. These resins can be suitably used because they are excellent in stretchability.

Specific examples of the polyester resin other than the polyethylene terephthalate and the copolymer thereof include polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, Hexane dimethyl terephthalate, and polycyclohexanedimethanol naphthalate.

The base film may be composed of one kind of polyester resin, or may be composed of a mixture of two or more kinds of polyester resins or a copolymer of two or more kinds of polyester resins.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.) . Preferably, a polymer containing as a main component a poly (meth) acrylate C _1-6 alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100 wt% By weight based on the total weight of the resin composition) is used.

The base film may be composed of one kind of (meth) acrylic resin, or may be composed of a mixture of two or more (meth) acrylic resins or a copolymer of two or more kinds of (meth) acrylic resins .

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate and the like. Also, examples thereof include copolymers thereof and those obtained by modifying a part of hydroxyl groups with other substituents. Of these, cellulose triacetate (triacetylcellulose) is particularly preferable. Many products of cellulose triacetate are commercially available and are advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate include all trade names such as &quot; Fuji Tack TD80 &quot; (manufactured by Fuji Film), Fuji Tack TD80UF (manufactured by Fuji Film), Fuji Tack TD80UZ (Manufactured by Konica Minolta Opt Co., Ltd.) and "KC4UY" (manufactured by Konica Minolta Opt Co., Ltd.), and the like.

The base film may be composed of one kind of cellulose ester resin, or may be composed of a mixture of two or more kinds of cellulose ester resins or a copolymer of two or more kinds of cellulose ester resins.

The polycarbonate resin is an engineering plastic composed of a polymer having a monomer unit bonded through a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy and transparency. The polycarbonate resin constituting the base film may be a resin called a modified polycarbonate such as a polymer skeleton modified to lower the photoelastic coefficient or a copolymerized polycarbonate improved in wavelength dependency.

Various products of polycarbonate resin are commercially available. Examples of commercially available products of the polycarbonate resin include trade names such as "Panlite" (manufactured by Deijin Kasei Co., Ltd.), "Yuferon" (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), "SD Polycar" (Manufactured by Dow Chemical Co., Ltd.) and "Kaliba" (manufactured by Dow Chemical Co., Ltd.).

The base film may be composed of one kind of polycarbonate resin or a mixture of two or more kinds of polycarbonate resins or a copolymer of two or more kinds of polycarbonate resins.

Of these, a polypropylene resin is preferably used from the viewpoint of stretchability and heat resistance.

In addition to the thermoplastic resin, any appropriate additives may be added to the base film. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant. The content of the thermoplastic resin in the base film is preferably 50 to 100 wt%, more preferably 50 to 99 wt%, still more preferably 60 to 98 wt%, and particularly preferably 70 to 97 wt%. When the content of the thermoplastic resin in the base film is less than 50% by weight, high transparency and the like inherently possessed by the thermoplastic resin may not be sufficiently manifested.

The thickness of the base film can be suitably determined, but is generally 1 to 500 占 퐉, more preferably 1 to 300 占 퐉, further preferably 5 to 200 占 퐉, from the viewpoint of workability such as strength and handling properties, And most preferably 5 to 150 mu m.

(Drying of coating layer and polyvinyl alcohol-based resin layer)

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 2 to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed on only one side of the base film or on both sides. It is possible to suppress the curling of the film that may occur during the production of the polarizing laminated film or the polarizing plate and to obtain two polarizing plates from one polarizing laminated film, It is advantageous.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 30 탆, more preferably 5 to 20 탆. In the case of a polyvinyl alcohol-based resin layer having a thickness within this range, a polarizing layer having good dyability and excellent polarizing performance and having a sufficiently small thickness can be obtained through a stretching step S30 and a dyeing step S40 described later have. If the thickness of the polyvinyl alcohol-based resin layer exceeds 30 占 퐉, the thickness of the polarizer layer may exceed 10 占 퐉. If the thickness of the polyvinyl alcohol-based resin layer is less than 3 占 퐉, the layer tends to become too thin after stretching to deteriorate the dyeability.

In order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer prior to coating of the coating liquid, at least the surface of the base film on which the polyvinyl alcohol-based resin layer is formed is subjected to corona treatment, plasma treatment, ) Treatment may be performed.

In order to improve adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin layer may be formed on the base film through a primer layer or an adhesive layer.

(Primer layer)

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of a base film and then drying it. The coating solution for forming a primer layer includes a component exhibiting a strong adhesion to some extent to both the base film and the polyvinyl alcohol-based resin layer. The coating solution for forming a primer layer usually contains a resin component and a solvent which give such adhesion. As the resin component, a thermoplastic resin having excellent transparency, thermal stability and stretchability is preferably used. Examples thereof include (meth) acrylic resin, polyvinyl alcohol resin and the like. Among them, a polyvinyl alcohol-based resin which gives good adhesion is preferably used.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and derivatives thereof. Examples of derivatives of polyvinyl alcohol resins include polyvinyl formal, polyvinyl acetal and the like, modified polyvinyl alcohol resins with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid; Acrylamide, and the like. Of the polyvinyl alcohol-based resins described above, polyvinyl alcohol resins are preferably used.

As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene and xylene; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Esters such as ethyl acetate and isobutyl acetate; Chlorinated hydrocarbons such as methylene chloride, trichlorethylene, and chloroform; Ethanol, 1-propanol, 2-propanol, and 1-butanol. However, when a primer layer is formed using a coating solution for forming a primer layer containing an organic solvent, the base film may be dissolved, so it is preferable to select a solvent in consideration of the solubility of the base film. Considering the environmental impact, it is preferable to form the primer layer with a coating solution containing water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming a primer layer. As the crosslinking agent, an appropriate one among known ones such as an organic type and an inorganic type is appropriately selected depending on the kind of the thermoplastic resin to be used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

As the epoxy-based crosslinking agent, any one of a one-liquid curing type and a two-liquid curing type may be used, and ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di- or tri- glycidyl ether, Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine and the like.

Examples of the isocyanate cross-linking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane) triisocyanate, isophorone diisocyanate, Block water or phenol block water.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, glutarialdehyde, maleindialdehyde, phthalaldehyde and the like.

Examples of the metal-based cross-linking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. Examples of the metal salt, metal oxide and metal hydroxide include salts of metals having a valence of 2 or more such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, Oxides and hydroxides.

The organometallic compound is a compound having at least one structure in which an organic group is directly bonded to a metal atom or an organic group is bonded through an oxygen atom or a nitrogen atom. The organic group means a monovalent or multivalent group containing at least a carbon element, and may be, for example, an alkyl group, an alkoxy group, an acyl group, or the like. The term &quot; bond &quot; means not only a covalent bond but also a coordination bond by coordination of a chelate-type compound or the like.

Suitable examples of the organometallic compound include an organic titanium compound, an organic zirconium compound, an organoaluminum compound, and an organosilicon compound. The organometallic compound may be used alone, or two or more of them may be used in combination.

Examples of the organic titanium compound include titanium ortho esters such as tetra n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, and tetramethyl titanate; Titanium chelates such as titanium acetylacetonato, titanium tetraacetylacetonato, polytitanacetylacetonato, titanium octylen glycolate, titanium lactate, titanium triethanolamine and titanium ethylacetoacetate; And titanium acylates such as polyhydroxytitanium stearate.

Examples of the organic zirconium compound include zirconium n-propionate, zirconium n-butyrate, zirconium tetraacetylacetonato, zirconium monoacetylacetonato, zirconium bisacetylacetonato, and zirconium acetylacetonatobis ethyl acetoacetate.

Examples of the organoaluminum compound include aluminum acetylacetonato and aluminum organic acid chelate. As the organosilicon compound, for example, there can be mentioned a compound in which the ligand exemplified above in the organic titanium compound and the organic zirconium compound is bonded to silicon.

In addition to the low molecular weight crosslinking agents described above, high molecular weight crosslinking agents such as methylol melamine resins and polyamide epoxy resins may also be used. Examples of commercial products of polyamide epoxy resin include "Sumirez Resin 650 (30)" and "Sumirez Resin 675" (both trade names) sold by Daoka Kagaku Kogyo Co., Ltd.

When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, a polyamide epoxy resin, a methylol melamine resin, a dialdehyde-based cross-linking agent, a metal chelate-based cross-linking agent and the like are suitably used as a cross-linking agent.

The ratio of the resin component and the crosslinking agent in the coating liquid for forming the primer layer may be appropriately determined in accordance with the kind of the resin component and the kind of the crosslinking agent, etc., in the range of about 0.1 to 100 parts by weight of the crosslinking agent, Particularly preferably about 0.1 to 50 parts by weight. The coating solution for forming a primer layer preferably has a solid concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably about 0.05 to 1 mu m, more preferably 0.1 to 0.4 mu m. If the thickness is smaller than 0.05 탆, the effect of improving the adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and if it is thicker than 1 탆, it is disadvantageous for thinning of the polarizing laminated film or polarizing plate.

The method of coating the primer layer-forming coating solution on the base film may be the same as that of the coating solution for forming the polyvinyl alcohol-based resin layer. The primer layer is applied to the surface (one surface or both surfaces of the base film) onto which the coating solution for forming the polyvinyl alcohol-based resin layer is coated. The drying temperature and the drying time of the coating layer composed of the coating solution for forming the primer layer are set according to the type of the solvent contained in the coating solution. The drying temperature is, for example, 50 to 200 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 30 seconds to 20 minutes.

(Subtract)

In the coating solution preparing step S10 and the resin layer forming step S20 described above, the coating solution is fed at least once through the pipe, and a part of the coating solution is taken out from the middle of the pipe.

When the coating liquid is prepared in the next resin layer forming step S20, the coating liquid containing bubbles may be supplied onto the base film from the coating head 5 The following cases can be specifically exemplified.

(A) When sucking of bubbles is confirmed in the coating liquid in the supplied storage tank 2 or in the coating liquid in the container connected to the pump 3 (for example, by the above-mentioned method (a) When the coating liquid is transferred, it is likely to be mixed with air to cause bubbles).

(B) When a coating liquid is supplied in the above-mentioned method (c) (air is mixed into the storage tank (2) or the container is likely to be foamed).

The amount of the coating liquid containing bubbles is supplied from the coating head 5 of the coating machine 1 at the time of coating the coating liquid in the next resin layer forming step S20, Time) can be effectively shortened (shortened), so that the loss of the base film can be greatly reduced, and a polarizing laminated film or polarizing plate can be produced with good yield.

The case where the liquid is drained in the resin layer forming step S20 is a case where there is a possibility that a coating liquid containing bubbles is supplied onto the base film from the coating head 5 at the time of coating the coating liquid, The case where the coating liquid is transferred through the inner space which is not filled with the coating liquid as the inner space of the first pipe 6 as when the coating is started. Even in such a case as well, since the amount (time) in which the coating liquid containing bubbles is supplied from the coating head 5 of the coating machine 1 can be effectively reduced (shortened), the loss of the base film can be greatly It is possible to produce a polarizing laminated film or a polarizing plate with good yield.

The liquid removal may be carried out only in the coating solution preparing step S10, in the resin layer forming step S20 only, or in both steps.

In the coating solution preparation step S10, when the coating solution is transferred to the storage tank 2 by the above-described method (a) through a piping using a pump or the like, a branch is provided in the middle of the piping, A part of the coating liquid can be removed.

In the coating solution preparation step S10, a part of the coating solution may be withdrawn between the storage tank 2 and the coating head 5 in the coating machine 1 when bubbles are generated in the coating solution in the storage tank in preparation. A part of the coating liquid in the coating machine 1 can be pulled out between the storage tank 2 and the coating head 5 in the coating machine 1 in the resin layer forming step S20. Hereinafter, a specific mode of extracting a part of the coating liquid between the storage tank 2 and the coating head 5 in the coating machine 1 will be described in more detail with reference to FIG.

The coating liquid is supplied from the storage tank 2 through the coating head 5 onto the base film. The coating liquid containing a lot of bubbles is taken out from the upstream side of the coating head. That is, a portion of the coating liquid is withdrawn at a position between the storage tank 2 and the coating head 5 while the pump 3 is operated to convey the coating liquid from the storage tank 2 toward the coating head 5. [ Specifically, as shown in Fig. 2, a second pipe 7 branched from the first pipe 6 is installed at any position between the storage tank 2 and the coating head 5, A method of extracting the coating liquid through the second pipe 7 can be suitably used. The coating liquid withdrawn from the second pipe 7 may be returned to the storage tank 2 for reuse after defoaming treatment if necessary.

If a flow path switching means such as a three-way cock is provided at a connection point between the first pipe 6 and the second pipe 7, the liquid draining and coating on the base film can be easily switched. The determination of this change is made by visually confirming the bubble state of the coating liquid discharged from the second pipe 7 (for example, when the coating liquid containing no bubbles starts to be discharged and the discharging is stopped, Or the like), or by automatic control.

The position where the first piping 6 and the second piping 7 are connected is set as close as possible to the coating head 5 so that the possibility of bubbling is lowered until the coating liquid reaches the coating head 5 from that position , And it is more preferable to be disposed on the downstream side (between the filter 4 and the coating head 5) than the filter 4 as shown in Fig. When the second pipe 7 is connected to the upstream side of the filter 4, bubbles may be generated when the coating liquid is supplied again to the filter 4 after finishing the draining. In order to prevent this, when the second pipe 7 is connected to the upstream side of the filter 4, it is preferable to carry out a treatment for removing the air in the filter 4 after the liquid is drained. On the other hand, two or more branch points to the second pipe 7 and two or more second pipes 7 may be provided between the storage tank 2 and the coating head 5.

The shape or material of the pipe of the second pipe 7 is not particularly limited as long as it does not interfere with the flow of the coating liquid in the first pipe 6, and may be a general pipe.

[3] Stretching step S30

This step is a step of obtaining a stretched film by stretching a laminated film comprising a base film and a polyvinyl alcohol-based resin layer. The stretching magnification of the laminated film can be appropriately selected in accordance with the desired polarization characteristics, and is preferably 5 times or more and 17 times or less, more preferably 5 times or more and 8 times or less the original length of the laminated film . If the stretching magnification is 5 times or less, the degree of polarization of the polarizer layer may not be sufficiently increased because the polyvinyl alcohol-based resin layer is not sufficiently oriented. On the other hand, if the stretching magnification exceeds 17 times, the film tends to be broken at the time of stretching, and the thickness of the stretched film becomes thinner than necessary, which may lower the workability and handleability in subsequent steps. The stretching treatment is usually uniaxial stretching.

The stretching treatment is not limited to stretching in one stage but may be performed in multiple stages. In this case, all of the multi-stage drawing process may be performed continuously before the dyeing process S40, and the drawing process after the second step may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process S40. In such a multi-stage stretching treatment, it is preferable that the stretching process is performed so that the overall stretching process steps are combined so that the stretching ratio exceeds 5 times.

The stretching treatment may be longitudinal stretching in which stretching is performed in the longitudinal direction of the film (film transport direction), transverse stretching or oblique stretching in stretching in the film width direction, or the like. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck. The transverse stretching method includes a tenter method and the like. Any of the wet drawing method and the dry drawing method can be employed for the drawing treatment, but a dry drawing method is preferable because the drawing temperature can be selected in a wide range.

The stretching temperature is set to a temperature higher than the temperature at which the entirety of the polyvinyl alcohol-based resin layer and the substrate film can be stretched to exhibit fluidity, and is preferably set at a melting point of the base film - 30 ° C , More preferably in the range of [melting point of base film-30] ° C [melting point of base film + 5] ° C, more preferably at [melting point of base film-25] Lt; 0 &gt; C. When the base film is composed of a plurality of resin layers, the melting point means the highest melting point among the melting points of the plurality of resin layers.

If the stretching temperature is lower than [the melting point of the base film-30] 占 폚, the stretching at a high magnification exceeding 5 times is difficult to achieve, or the flowability of the base film is too low to make the stretching process difficult. If the stretching temperature exceeds the melting point of the base film + 30 ° C, the fluidity of the base film tends to be excessively large and the stretching tends to be difficult. The stretching temperature is within the above range, more preferably 120 deg. C or more, since it is easier to achieve a high draw ratio of more than 5 times. When the stretching temperature is 120 ° C or higher, even if the stretching magnification exceeds 5 times, there is no difficulty in stretching treatment.

As the heating method of the laminated film in the stretching treatment, a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace in which hot air is blown and adjusted to a predetermined temperature); A method of heating the roll itself in the case of stretching using a roll; A heater heating method (a method of heating an infrared heater, a halogen heater, a panel heater, and the like on the laminated film and heating it by radiant heat). In the roll-to-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature. In this case, the two nip roll pairs may be provided in the stretching zone controlled by humidity or may be provided outside the stretching zone, but it is preferable that the two nip roll pairs are provided outside the stretching zone to prevent adhesion between the laminated film and the nip roll.

On the other hand, the stretching temperature means the atmosphere temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and the atmosphere temperature in the furnace in the case of heating in the furnace in the heater heating method. In the case of the method of heating the roll itself, it means the surface temperature of the roll.

Prior to the stretching step S30, a preheating treatment step for preheating the laminated film may be performed. As the preheating method, the same method as the heating method in the stretching treatment can be used. In the case where the stretching treatment method is roll-to-roll stretching, preheating may be performed at any timing before passing through the nip roll on the upstream side, during passing, and after passing. When the stretching treatment method is thermal roll stretching, preheating is preferably performed at a timing before passing through the thermal roll. When the stretching treatment method is stretching using a chuck, preheating is preferably performed at a timing before the chuck distance is widened. The preheating temperature is preferably in the range of -50 占 폚 to 占 0 占 폚 of the stretching temperature, and more preferably in the range of [stretching temperature -40] 占 폚 - [stretching temperature-10] 占 폚.

After the stretching process in the stretching process S30, a heat fixing process may be performed. The heat fixation treatment is a process in which heat treatment is performed at a crystallization temperature or higher while keeping the end portion of the stretched film in a state of being held in a state of being held by a clip. By the heat-setting treatment, the crystallization of the polyvinyl alcohol-based resin layer is promoted. The temperature of the heat setting treatment is preferably in the range of -0 ° C to -80 ° C of the drawing temperature, and more preferably in the range of [drawing temperature -0] ° C to [drawing temperature -50 ° C].

[4] Dyeing Step S40

In this step, the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye, and the dyed dye is adsorbed and oriented to form a polarizer layer. A polarizing laminated film in which a polarizer layer is laminated on one side or both sides of a base film through this step can be obtained.

Specific examples of the dichroic dye include iodine and dichroic organic dyes. Specific examples of the dichroic organic dyes include red BR, red LR, red R, pink LB, rubin BL, Borde GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB , Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Orange S, and First Black. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

The dyeing step can be carried out by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution obtained by dissolving the dichroic dye in a solvent can be used. As the solvent of the dyeing solution, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10 wt%, more preferably 0.02 to 7 wt%, and still more preferably 0.025 to 5 wt%.

When iodine is used as the dichroic dye, the dyeing efficiency can be further improved. Therefore, it is preferable to add iodide to the dyeing solution containing iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80, To 1: 70.

The time for immersing the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 占 폚, and more preferably in the range of 20 to 40 占 폚.

On the other hand, the stretched film may be further subjected to stretching treatment during the dyeing step S40. Examples of this embodiment include: 1) a mode in which the stretching process is performed so that the total draw ratio becomes the target multiple during the dyeing process in the dyeing process S40, 2) In the drawing step S30, after the drawing processing is performed at a lower magnification than the target, the total drawing magnification is changed to the target magnification during the dyeing processing in the dyeing step S40, as described later And then the stretching treatment is carried out to such an extent that the final total stretching magnification is equal to the target magnification.

The dyeing step S40 may include a crosslinking treatment step which is carried out subsequent to the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known materials can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

Specifically, the crosslinking solution may be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water may be used, but an organic solvent which is compatible with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20 wt%, and more preferably in the range of 6 to 15 wt%.

The crosslinking solution may comprise iodide. By adding iodide, the polarization performance in the plane of the polarizer layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide iodide. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The time for immersing the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes. The temperature of the crosslinking solution is preferably in the range of 10 to 90 占 폚.

On the other hand, the crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing solution. The stretching treatment may be performed during the crosslinking treatment. The specific embodiment in which the stretching treatment is carried out during the crosslinking treatment is as described above.

After the dyeing step S40, it is preferable to carry out a cleaning step and a drying step before the bonding step S50 to be described later. The cleaning process usually includes a water cleaning process. The water rinsing treatment can be performed by immersing the film after dyeing the pure water such as ion-exchanged water or distilled water, or after crosslinking treatment. The water washing temperature is usually in the range of 3 to 50 캜, preferably 4 to 20 캜. The immersion time in water is usually from 2 to 300 seconds, preferably from 3 to 240 seconds.

The cleaning step may be a combination of a water cleaning step and a cleaning step with an iodide solution. In addition to water, a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, and propanol may suitably be contained in the washing liquid used in the water washing step and / or the washing treatment with the iodide solution.

As the drying step performed after the cleaning step, any suitable method such as natural drying, air blow drying, and heat drying can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C, and the drying time is usually about 1 to 15 minutes. The polarizing laminated film obtained as described above can be used as a polarizing element as it is, and is also useful as an intermediate for producing a polarizing plate comprising a polarizing layer and a protective film.

The thickness of the polarizer layer of the polarizing laminated film is 10 占 퐉 or less, preferably 7 占 퐉 or less. By setting the thickness of the polarizer layer to 10 m or less, a thin polarizing laminated film can be formed.

&Lt; Polarizing plate production method >

The method for producing a polarizing plate of the present invention comprises the steps of preparing the above-mentioned polarizing laminated film, a bonding step S50 of bonding a protective film on the polarizing layer of the polarizing laminated film to obtain a bonding film, peeling the base film from the bonding film And a peeling process S60 for removing the film.

[5] Bonding step S50

This step is a step of obtaining a bonded film by bonding a protective film on the polarizer layer of the polarizing laminated film, that is, the surface of the polarizer layer opposite to the base film side. The protective film can be bonded to the polarizer layer using an adhesive or a pressure-sensitive adhesive. When the polarizing laminated film has polarizer layers on both sides of the base film, the protective film is usually bonded on the polarizer layers on both sides. In this case, these protective films may be the same kind of protective film or different kinds of protective films.

(Protective film)

Examples of the protective film include polyolefin resins such as a chain polyolefin resin (polypropylene resin and the like) and a cyclic polyolefin resin (norbornene resin and the like); Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins; Or a mixture or copolymer thereof, or the like. Examples of usable commercially available products such as a cyclic polyolefin resin and a film thereof, and cellulose triacetate are the same as those described above.

The protective film may be a protective film having an optical function such as a retardation film, a brightness enhancement film and the like. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching or biaxially stretching) a resin film made of the above material, or forming a liquid crystal layer or the like on the film.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface of the protective film opposite to the polarizer layer. Methods for forming these optical layers on the surface of the protective film are not particularly limited, and known methods can be used. The optical layer may be formed beforehand on the protective film before the bonding step S50, or may be formed after the bonding step S50 or after the peeling step S60 described later.

In bonding the protective film on the polarizer layer, the surface of the protective film on the polarizer layer side may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment (This adhesion treatment) can be carried out. Among them, plasma treatment, corona treatment or saponification treatment is preferably carried out. For example, when the protective film is made of a cyclic polyolefin resin, a plasma treatment or a corona treatment is usually performed. In the case of a cellulose ester resin, saponification treatment is usually carried out. As the saponification treatment, there may be mentioned a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

Though the thickness of the protective film is preferably small, if it is too thin, the strength is lowered and the workability is poor. On the other hand, if the thickness is excessively large, there arises a problem that the transparency is lowered and the curing time required after bonding is prolonged. Therefore, the thickness of the protective film is preferably 90 占 퐉 or less, more preferably 5 to 60 占 퐉, and still more preferably 5 to 50 占 퐉. From the viewpoint of thinning of the polarizing plate, the total thickness of the polarizing layer and the protective film is preferably 100 占 퐉 or less, more preferably 90 占 퐉 or less, further preferably 80 占 퐉 or less.

(glue)

As the adhesive, an aqueous adhesive or a photo-curable adhesive can be used. Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component emulsion type urethane emulsion adhesive, and the like. Particularly when a cellulose ester based resin film that has been surface-treated (hydrophilized) by saponification treatment or the like is used as the protective film, it is preferable to use an aqueous adhesive composed of a polyvinyl alcohol-based resin aqueous solution.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol-based copolymers obtained by saponifying a copolymer of vinyl acetate and other monomers copolymerizable therewith, as well as a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, Or a modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl group of these polymers. The water-based adhesive may include additives such as polyvalent aldehyde, water-soluble epoxy compound, melamine compound, zirconia compound, and zinc compound. When an aqueous adhesive is used, the thickness of the adhesive layer obtained therefrom is usually 1 占 퐉 or less.

A bonding process is carried out by coating an aqueous adhesive on the polarizer layer of the polarizing laminated film and / or on the protective film, joining these films through the adhesive layer, and preferably by pressing using a bonding roll or the like. The coating method of the water based adhesive (the same applies to the photo-curing adhesive) is not particularly limited, and the coating method such as the softening method, Meyer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, dip coating method, Conventionally known methods can be used.

When an aqueous adhesive is used, it is preferable to carry out a drying step of drying the film in order to remove water contained in the water-based adhesive after the above-described bonding. Drying can be performed, for example, by introducing a film into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 占 폚. If it is less than 30 DEG C, the protective film tends to be easily peeled from the polarizer layer. When the drying temperature exceeds 90 ° C, there is a fear that the polarization performance of the polarizer layer is deteriorated by heat. The drying time can be about 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, more preferably 150 to 600 seconds.

After the drying step, a curing step may be performed at a temperature of room temperature or slightly higher, for example, at a temperature of about 20 to 45 DEG C for about 12 to 600 hours. The curing temperature is generally set to be lower than the drying temperature.

The photo-curing adhesive refers to an adhesive that cures by irradiating active energy rays such as ultraviolet rays. Examples of the adhesive include a polymerizable compound and a photopolymerization initiator, a photoreactive resin, a binder resin and a photoreactive crosslinking agent And the like. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer and a photocurable urethane monomer, and oligomers derived from a photopolymerizable monomer. Examples of the photopolymerization initiator include materials which generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy-based monomer and a photocationic polymerization initiator can be preferably used.

In the case of using a photo-curable adhesive, a curing step of curing the photo-curing adhesive by irradiating an active energy ray followed by a drying step (if the photo-curable adhesive contains a solvent, etc.) . A light source of an active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, A wave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity to the photo-curable adhesive is suitably determined according to the composition of the photo-curable adhesive, and it is preferable that the irradiation intensity in the wavelength range effective for activating the polymerization initiator is set to 0.1 to 6000 mW / cm 2. When the irradiation intensity is not less than 0.1 mW / cm 2, the reaction time does not become too long. When the irradiation intensity is not more than 6000 mW / cm 2, the heat radiated from the light source and the yellowing of the photocurable adhesive due to heat generation during curing of the photo- There is little fear of causing deterioration.

It is preferable that the light irradiation time to the photo-curable adhesive is appropriately determined according to the composition of the photo-curable adhesive and is set so that the integrated light quantity represented by the irradiation intensity and the irradiation time is 10 to 10000 mJ / cm 2 Do. When the accumulated light quantity is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be generated sufficiently to allow the curing reaction to proceed more surely. When the total amount is 10,000 mJ / cm 2 or less, the irradiation time is not excessively long, .

On the other hand, the thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 mu m, preferably 0.01 to 2 mu m, more preferably 0.01 to 1 mu m.

(adhesive)

The pressure-sensitive adhesive that can be used for bonding the protective film is usually composed of a pressure-sensitive adhesive composition in which an acrylic resin, a styrene resin, a silicone resin, or the like is used as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto. It is also possible to use a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer may be 1 to 40 占 퐉, but it is preferable that the pressure-sensitive adhesive layer is thinly coated within the range not deteriorating the workability and durability characteristics, and more preferably 3 to 25 占 퐉. A thickness of 3 to 25 占 퐉 has favorable workability and is also suitable for suppressing the dimensional change of the polarizer layer. When the pressure-sensitive adhesive layer is less than 1 탆, the pressure-sensitive adhesive property tends to deteriorate, and when the pressure-sensitive adhesive layer is more than 40 탆, the pressure-sensitive adhesive is likely to be discharged. In the method of bonding the protective film to the polarizer layer using the pressure-sensitive adhesive, the pressure-sensitive adhesive layer may be formed on the protective film surface and then bonded to the polarizer layer. Alternatively, a pressure-sensitive adhesive layer may be formed on the polarizer layer surface, It may be bonded.

The method of forming the pressure-sensitive adhesive layer is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing the above-mentioned base polymer and the above-mentioned components is coated on the surface of the protective film or the surface of the polarizer layer, The protective film and the polarizer layer may be bonded to each other. After the pressure-sensitive adhesive layer is formed on the separator (release film), the pressure-sensitive adhesive layer is transferred onto the protective film surface or the polarizing film surface, As shown in Fig. When the pressure-sensitive adhesive layer is formed on the protective film surface or the polarizer layer surface, surface treatment such as corona treatment or the like may be carried out on one side or both sides of the protective film surface or the polarizer layer side or the pressure-

[6] Peeling step S60

This step is a step of peeling off a base film from a bonding film obtained by bonding a protective film. Through this process, a polarizing plate in which a protective film is laminated on the polarizing layer can be obtained. When the polarizing laminated film has polarizer layers on both sides of the base film and a protective film is bonded to both polarizer layers, two polarizing plates can be obtained from one polarizing laminated film by the peeling step S60 .

The method of peeling off the base film is not particularly limited, and can be peeled off in the same manner as the peeling process of a separator (peeling film) made of a polarizing plate having a usual pressure-sensitive adhesive. The base film may be peeled off immediately after the bonding step S50, or it may be rolled up into a roll once after the bonding step S50, and peeled off in the subsequent step.

The polarizing plate thus produced may be used as an optical film in which other optical layers are laminated in actual use. Further, the protective film may have the function of such an optical layer. As another optical layer, a reflective polarizing film that transmits polarized light of a certain kind and reflects polarized light exhibiting properties opposite to that of the polarized light; A film having an antireflection function on the surface and having an antiglare function; A film having a surface antireflection function; A reflecting film having a reflecting function on the surface; A transflective film having a reflection function and a transmission function; And a viewing angle compensation film.

Examples of commercial products corresponding to reflective polarizing films that transmit polarized light of a certain kind through polarized light and exhibit properties opposite to those of polarized light include those commercially available from &quot; DBEF &quot; (manufactured by 3M, Sumitomo 3M APF &quot; (available from 3M Company, Japan, available from Sumitomo 3M Ltd.).

Examples of the viewing angle compensation film include an optical compensation film on which a liquid crystal compound is applied and aligned and fixed on the substrate surface, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin.

As commercial products corresponding to optical compensation films on which a liquid crystal compound is applied and fixed on the surface of the base material, there are WV film (manufactured by Fuji Film Co., Ltd.), NH film (manufactured by JX Nikkisseiki Energy Co., ), And &quot; NR film &quot; (manufactured by JX Nikkoseki Energy Co., Ltd.).

Examples of commercially available products corresponding to the retardation film made of the cyclic polyolefin resin include "Aton film" (manufactured by JSR Corporation), "Essen" (manufactured by Sekisui Gakugei Kogyo Co., Ltd.), "Zeonoa Film" (Manufactured by Zeon Corporation).

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

&Lt; Example 1 >

(1) Production of base film

A homopolymer of propylene (hereinafter referred to as &quot; propylene homopolymer &quot;) was laminated on both sides of a resin layer composed of a random copolymer of propylene / ethylene containing about 5% by weight of an ethylene unit (&quot; Sumitomonobrene W151 &quot;, manufactured by Sumitomo Chemical Co., (Sumitomonbrene FLX80E4, manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 占 폚) was disposed on the entire surface of the base material film by coextrusion molding using a multilayer extrusion molding machine . The total thickness of the base film was 100 占 퐉, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

(2) Preparation of coating liquid

A polyvinyl alcohol powder ("Z-200", manufactured by Nippon Gosei Chemical Industry Co., Ltd., average polymerization degree: 1100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C and a polyvinyl alcohol aqueous solution . The obtained aqueous solution was mixed with 1 part by weight of a crosslinking agent (&quot; Sumirez Resin 650 &quot; manufactured by Daoka Kagaku Kogyo Co., Ltd.) per 2 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Further, a polyvinyl alcohol powder ("PVA 124" manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, average degree of saponification: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8% And this was used as a coating solution for forming a polyvinyl alcohol-based resin layer.

(3) Execution of drainage

The coating liquid for forming a polyvinyl alcohol-based resin layer was transferred to a reservoir of a comma coater using a pump. As shown in Fig. 2, the comma coater is provided with a second piping for draining between a filter for trapping dust and a coating head, and a moving destination of the coating solution passing through the first piping Piping) can be switched using a three-way cock. Subsequently, in a state where the three-way cock was switched to the second pipe side, the pump of the comma coater was operated to feed the coating liquid in the storage tank in the direction of the coating head through the first pipe, and discharged from the second pipe . The amount of bubbles originally released into the discharged coating liquid was confirmed when the bubbles were visually observed, but the amount of bubbles decreased with the increase of the emission amount. At the time when it was judged that the amount of bubbles was sufficiently small, the three-way cock was switched, the coating liquid was fed to the coating head, and the pump was once stopped.

(4) Formation of primer layer and polyvinyl alcohol-based resin layer

The corona-treated surface of one side of the base film produced in the above (1) was continuously conveyed, and the coating solution for forming the primer layer was continuously coated on the corona-treated side using a micro gravure coater, And dried at 60 DEG C for 3 minutes to form a primer layer having a thickness of 0.2 mu m. Subsequently, the coating solution was continuously coated on the primer layer using the above-described comma coater filled with the coating solution for forming a polyvinyl alcohol-based resin layer up to the coating head while conveying the film, Lt; 0 &gt; C for 3 minutes and then dried at 60 DEG C for 4 minutes to form a polyvinyl alcohol-based resin layer having a thickness of 11.0 mu m on the primer layer.

Immediately after the start of coating of the coating solution for forming a polyvinyl alcohol-based resin layer, the foam spilled out onto the coated surface, but the outflow was immediately absorbed, and the loss of the substrate film hardly occurred.

The surface of the substrate film opposite to the surface on which the polyvinyl alcohol resin layer was formed was subjected to the same treatment as described above to sequentially form a primer layer and a polyvinyl alcohol resin layer, And a polyvinyl alcohol-based resin layer having a thickness of 11.0 占 퐉 were formed to obtain a laminated film composed of a polyvinyl alcohol-based resin layer / primer layer / base film / primer layer / polyvinyl alcohol-based resin layer.

When the coating liquid for forming a polyvinyl alcohol-based resin layer was coated on the surface of the substrate film on the opposite side, the outflow of the foam immediately after the coating was started was not recognized even if the liquid removal was not carried out. This is because the coating liquid containing no bubbles is filled up to the coating head.

(5) Stretching of laminated film

The laminated film obtained in the above (4) was subjected to free stretching at a stretching ratio of 5.5 times in the machine direction (film transport direction) at a stretching temperature of 160 캜 by a nip roll stretching method while continuously transporting the stretched film. The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 5.5 占 퐉 on one side and 5.3 占 퐉 on the other.

(6) Production of polarizing laminated film

The stretched film prepared in the above step (5) was continuously transported and immersed in a hot water bath at 60 DEG C for 60 seconds so that the retention time was 150 seconds in a dyeing solution at 30 DEG C containing iodine and potassium iodide So that the polyvinyl alcohol-based resin layer was subjected to a dyeing treatment, and then the excess dyeing solution was washed away from pure water at 10 占 폚. Subsequently, the substrate was immersed in a crosslinked solution at 76 DEG C containing boric acid and potassium iodide so that the residence time would be 600 seconds, followed by crosslinking treatment. Thereafter, the film was washed with pure water at 10 占 폚 for 4 seconds and dried at 80 占 폚 for 300 seconds to produce a polarizing laminated film.

(7) Production of Polarizing Plate

A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared by dissolving polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average degree of polymerization: 1800) in hot water at 95 ° C. The obtained aqueous solution was mixed with 1 part by weight of a crosslinking agent ("Sumirez Resin 650" manufactured by Daoka Kagaku Kogyo Co., Ltd.) per 2 parts by weight of the polyvinyl alcohol powder to obtain an aqueous adhesive solution.

Subsequently, while the polarizing laminated film prepared in (6) was continuously conveyed, the adhesive aqueous solution was coated on both polarizer layers, and then a protective film (triacetylcellulose (TAC) (KC4UY, manufactured by Konica Minolta Opt.) Having a thickness of 40 占 퐉) was bonded on the polarizer layer and passed through between the pair of bonding rolls to form a TAC / polarizer layer / primer layer / A laminated film comprising a base film, a primer layer, a polarizer layer and a TAC layer was produced.

Then, the bonding film was peeled off at the interface between the base film and the primer layer to obtain a polarizing plate comprising a TAC / polarizer layer / primer layer / base film and a primer layer / polarizer layer / TAC, The base film was peeled off from the film to obtain another polarizing plate. In the step of peeling the base film, no problem such as breakage of the film occurred.

&Lt; Comparative Example 1 &

The primer layer and the polyvinyl alcohol-based resin layer were formed without removing the liquid of (3) in Example 1. When the application of the coating solution for forming a polyvinyl alcohol-based resin layer was started, the foam was leaked to the entire surface of the coated surface together with the coating solution. It took two hours until the outflow of bubbles was fixed, and the loss of the base film was large. On the other hand, when the coating liquid for forming a polyvinyl alcohol-based resin layer was coated on the surface of the base film on the opposite side, the outflow of bubbles immediately after the start of coating was not recognized.

According to the method of the present invention, since the loss of the base film can be reduced, a polarizing laminated film or a polarizing plate can be produced with good yield.

1: Paint machine, 2: Storage tank, 3: Pump, 4: Filter, 5: Coating head, 6: First piping, 7: Second piping.

Claims (8)

A coating liquid preparation step of preparing a coating liquid containing a polyvinyl alcohol-based resin in a reservoir of a coating machine;
The coating liquid is supplied from at least one surface of the base film through the coating head of the coating machine from the storage tank and is then dried to form a polyvinyl alcohol based resin layer to form a resin layer The process,
A stretching step of stretching the laminated film to obtain a stretched film,
A dyeing step of obtaining a polarizing laminated film by dying a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer
And,
Wherein the coating liquid is transferred at least once through a pipe in the coating liquid preparing step and / or the resin layer forming step, and a part of the coating liquid is taken out from the pipe during the step of preparing the polarizing laminated film. The coating apparatus according to claim 1, wherein the coating machine includes a first pipe connecting the storage tank and the coating head, and a second pipe branched from the first pipe,
And a part of the coating liquid is taken out through the second pipe while transferring the coating liquid from the storage tank toward the coating head. The production method according to claim 2, wherein the liquid subtracting step is carried out when the coating liquid is passed through the inner space of the first pipe having the inner space not filled with the coating liquid. The production method according to any one of claims 1 to 3, wherein the laminated film is stretched at a draw ratio of more than 5 times. The production method according to any one of claims 1 to 4, wherein in the resin layer forming step, the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film. The production method according to any one of claims 1 to 5, wherein the thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 to 30 탆. The production method according to any one of claims 1 to 6, wherein the base film is made of a polypropylene type resin. A method for producing a polarizing laminated film, comprising the steps of: preparing a polarizing laminated film by the production method according to any one of claims 1 to 7;
A step of bonding a protective film to the polarizer layer of the polarizing laminated film to obtain a bonded film,
A step of peeling the base film from the bonded film
And a polarizing plate.

Images